Death of neurons (apoptosis) occurs in both acute and chronic neurodegenerative diseases such as stroke, Alzheimer's, Parkinson's, and Huntington's diseases and is primarily mediated by activated cysteine proteases (caspases). Cascades of neuronal death emerge gradually, providing a period _vailable for therapeutic intervention. However, the widespread nature of the neuronal injury presents a ',onsiderable challenge to the development of therapeutic strategies. Several strategies were designed to _terrupt the apoptotic cascade but they are limited by problems related to toxicity or the failure to retain neuronal function, likely due to targeting of effectors that function late in the apoptotic cascade. Our )reliminary data indicate that a HSV-2 gene (ICP10PK) prevents apoptosis of CNS neurons in vitro rlduced by various stimuli. We constructed a growth-compromised HSV-2 mutant (ICP10 RR) that etains ICP10PK and anti-apoptotic activity, is not toxic following intrastriatal injection and disseminates to ;onnected sites in the CNS (including hippocampus) upon intranasal delivery. Neuroprotective potential invirus infected cells is due to activation of the Raf/MEK/ERK survival pathway. We propose to evaluate the therapeutic potential of ICP10 PK in acute excitotoxic injury in vivo and define the mechanism of anti-apoptotic activity. The specific aims are: (i) To examine the mechanism of ICP10 PK anti-apoptotic activity in paradigms represented by removal of trophic growth support or oxidative stress, (ii) To engineer vectors that target both both upstream (ICP10 PK) and downstream (XIAP or p35) apoptotic effectors and examine their anti-apopotic activity (relative to ICP10 RR) in organotypic cultures teated with kianic acid (excitotoxic model), (iii) To determine the ability of ICP10 RR and the XlAP/p35 mutants to prevent excitotoxic death in vivo, and (iv) To determine whether ICP10PK expression in the hippocampus maintains synaptic transmission and functional plasticity. The studies will provide significant information required for the development of ICP10PK based therapies for the treatment of acute and chronic neurodegenerative diseases that are associated with apoptosis.